Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full behavioral burden and does meaningful work: it discloses that only completed (not in-flight) checks are returned, that the call is free, and it defines the non-obvious "named" threshold (2 of 4 runs, at least one engine, at least one tracked question). It does not cover auth requirements, freshness/staleness of the latest check, or pagination behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

It front-loads what the tool returns and then supplies only the two definitions an agent actually needs (the stability label example and the "named" rule). Slightly dense with the inline quoted example and the final definition sentence, but no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema and no annotations, the description must carry the return-value burden, and it only sketches the shape (question/engine pairs, stability labels, named brands) without describing field structure or empty-state behavior when no check has finished. The cost signal and "named" definition help, but the picture remains partial.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline of 4 applies. The stability-label and "named" definitions add semantic meaning to the output fields even though no input exists.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific resource and scope: the latest *finished* full check, listing question/engine pairs with stability labels plus the brands named in your place. That is enough for an agent to know this is a retrieval of existing results rather than a new scan, though it never explicitly contrasts itself with the sibling visibility_run.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The word "Free" plus "latest finished" implies you call this to read results from an already-completed check instead of paying to run a new one, which is useful routing context. However, there is no explicit when-to-use/when-not statement and no direct pointer to visibility_run or what to do when no check has finished yet.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.